Success rate of informed consent acquisition and factors influencing participation in a multicenter randomized controlled trial of laparoscopic versus open surgery for stage II/III colon cancer in Japan (JCOG0404)

Introduction Successful completion of randomized controlled trials (RCT) is dependent on informed consent (IC) acquisition from patients. The aim of this study was to prospectively calculate the proportion of participation in a surgical RCT and to identify the reasons for failed IC acquisition. Methods A 30‐institute RCT was conducted to evaluate oncological outcomes of open and laparoscopic surgery for stage II/III colon cancer (JCOG0404: UMIN‐CTR C000000105). The success rate of obtaining IC, which was supported by a DVD that helped patients understand this trial, was evaluated in eight periods between October 2004 and March 2009. In addition, reasons for failed IC acquisition were identified from questionnaires. Results A total of 1767 patients were informed of their eligibility for the trial, and 1057 (60%) were randomly assigned to either the laparoscopic surgery (n = 529) or open surgery (n = 528) group. The success rate of IC acquisition ranged from 50% to 62% in eight periods. The most common reasons for failed IC acquisition were anxiety/unhappiness about the randomization, patients' preference for one form of surgery, and strong recommendations from referring doctors or relatives. Conclusions With the assistance of a DVD, high success rates of IC acquisition were obtained for an RCT of laparoscopic versus open surgery for stage II/III colon cancers. To obtain such a rate, investigators should make efforts to inform patients, their relatives, and referring doctors about the medical contributions a surgical RCT can make.